How do I interpret the results of the aldosterone-to-renin ratio in the context of diagnosing primary aldosteronism?

Interpretation of the aldosterone-to-renin ratio (ARR) in diagnosing primary aldosteronism (PA) requires understanding that a raised ARR is a sensitive screening indicator suggestive of PA, but must be interpreted in the clinical context and alongside confirmatory testing.

A high ARR reflects inappropriately elevated aldosterone relative to suppressed renin, which is characteristic of PA due to autonomous aldosterone secretion ¹. However, the absolute aldosterone and renin values, patient posture, medications, and potassium status can influence the ratio and must be considered to avoid false positives or negatives (Li et al., 2016; Schilbach et al., 2019).

UK guidelines recommend using the ARR as an initial screening tool in patients with hypertension and hypokalaemia or resistant hypertension, but emphasise that a raised ARR alone does not confirm PA; it necessitates confirmatory testing such as saline infusion or fludrocortisone suppression tests ¹.

Recent meta-analyses and studies support the ARR’s high sensitivity but variable specificity, highlighting the importance of standardised sampling conditions and interpretation thresholds tailored to the assay used (Hung et al., 2021; Li et al., 2016). They also note that direct renin concentration or plasma renin activity can be used, but results are not interchangeable and require assay-specific cut-offs (Schilbach et al., 2019).

In summary, a raised ARR should prompt further confirmatory testing rather than be used in isolation to diagnose PA. Interpretation must integrate clinical features, biochemical context, and assay-specific reference ranges to optimise diagnostic accuracy ¹ (Hung et al., 2021; Schilbach et al., 2019).